10. Allison Janney as Mother on LOST
One of the biggest twists of the final season of LOST was that the events of a series consisting almost exclusively of characters with daddy issues was set in motion by two immortals with extreme mommy issues. As the immortal adoptive mother of Jacob (Mark Pellegrino) and the Man in Black (Titus Welliver)—she stoned their mother to death after she gave birth to them—Mother basically used them to ease her eternal burden and become the protector of the Island, mentally turning them against each other with her oft-skewering favoritism.
When the Man in Black abandoned the plan and tried to leave the Island to find his true home, she destroyed his entire village and their work, through probable Smoke Monster-ish means, and enticed him to kill her—but not before laying her job on Jacob, setting in motion an eternity's worth of sibling rivalry that would claim the lives of many innocent people. She didn't need more than the one appearance—or a proper name—to make her eligible for top 10 worst mothers of all time. It's too bad she was stuck in one of the corniest episodes the show ever attempted.